WATER roles in cells: Biological and biophysical perspectives

Water, elected as Molecule of the Year by the American Society for Biochemistry and Molecular Biology, is the substance in which life originated on this planet and became then involved in numerous cell functions of all animal and vegetal tissues, up to being the most abundant component of all living systems. Despite its importance, however, the various conditions and roles of water in the protoplasm are mostly absent in current cell biology textbooks and common related reviews, so the subject demands consideration of how it should be now taught to graduate students interested in biochemistry and molecular biology. The present paper offers an overview of how knowledge about water involvement in cell structure and function has evolved from the mid 19th century up to our time, starting with early microscopic inspections of living cells, proceeding next to the emergence of notions about water distribution within them, including its various particular behaviors in the protoplasm and the roles it plays in cell function, plus succinct notes about recent reports of experimental approaches with their results and particular views on the topic for different types of cells.